Forum Replies Created
- October 14, 2021 at 9:00 am #8477
Hi. If B+ and B- are shorted, the sabertooth needs to be returned to Dimension Engineering for repair. SorryAugust 30, 2021 at 10:19 am #8465
Hey there Steve!
Welcome to the world of robotics, you’ve chosen a great time to get into this! Having hauled beach wagons I can sympathize, it’s definitely a drag. I’m going to try to go through your list of specifications and see if we can provide some advice.
We have a support wiki that has a section on building robots. It offers some information on the different components and a bit of advice on picking parts. Here’s a link to it!
First, the biggest challenge for you is going to be getting it waterproof and dust/sand proof. Any open points of the chassis will need gaskets/seals. You’ll want your charging port and switch to be waterproof or have waterproof covers. You’ll also want to either house your internal components inside a waterproof container or apply a coating of epoxy, silicon, or other material. Your motor shafts and their access points in the chassis will also be tricky in sand.
- A tracked chassis or 6-wheel drive system would be best for sand and off-road terrain.
- For the motors, payload, and speed, I’d recommend looking at our Tracked Chassis Payload/Speed chart. It shows some ranges you can expect to get out of different motors/chassis combinations. Even if you don’t use one of our base kits, it’s a great starting point to understand what motor would fit your needs.
- For distance you’ll want to pay attention to your battery system, making sure it has enough juice to go the distance. SLA is cheaper than LiFePO4 batteries but weighs a lot more.
- Obstacle/terrain should be fine on a tracked system as long as you make sure your chassis has a bit of ground clearance. Something like the HD2 system [/url] can handle curbs head-on.
- Control through an RC is easy enough to implement, we use the FlySky RC system for a lot of our robots and it’s reliable. Good range, multiple channels, and affordable.
Happy to have you join the robotics community Steve and we hope this helps!
-Ben at SuperDroidRobotsJuly 6, 2021 at 12:02 pm #8429
Sorry but we order the wheelchair motors already assembled and do not carry individual parts. Unfortunately if the part cannot be repaired you would need to order a new motor.June 24, 2021 at 8:50 am #8425
Hi Peter. Nice mower! It looks like its done well for you. The 2WD design does have its limitations. For hills a 4WD is the way to go. Here is a prototype 4WD that we built recently that is cutting on slopes up to 38 degrees.
As for being able to cut close to a fence, there are some tradeoffs to consider. We’re basically replacing the small, narrow wheels on a push mower with a bigger wheel that can be driven by a motor and get some traction. If you put the wheel in the same place its going to stick out past the deck. You could try putting the wheel behind the mower but in doing so you’ll have to make the robot quite a bit longer and you’ll lose some maneuverability.
Anyway, hope this helps and good luck on your next build.June 24, 2021 at 8:37 am #8424
I’m not familiar with this pipeline for controlling robot arms but it sounds like you can use grbl regardless since you’re on Arduino and you need to generate a pulsetrain for the stepper motors. I haven’t worked with Universal G Code Sender either but I think you’re right that this will be too restrictive for what you’re trying to do. The first stage of the project should be figuring out how to give speed commands for each stepper motor to grbl and figuring out the conversion factors to turn the pulse count and pulse rate into real angles and rotation rates in e.g. rad and rad/s and vice versa. Reading joystick axes, turning them into individual joint speeds, and passing them to grbl is a good start.
Ultimately with inverse kinematics, you are trying to place the correct acceleration/velocity on each joint to get a desired acceleration/velocity at the end effector. The necessary acceleration and velocity at each joint is a function of the current joint positions, so you will need to track the angle of each joint to accomplish this. You can track the number of pulses sent to the stepper motors but you will need some type of homing routine on boot so the joints are starting from a known position.June 15, 2021 at 9:49 am #8417
Yes, those motors can definitely be mounted horizontally as well. If you look at an electric wheelchair, that’s actually how they are mounted.May 24, 2021 at 8:48 am #8408
You can get chains to put the on the wheels. Converting to tracks would be a very difficult task… We have used chains before and it works well.May 19, 2021 at 8:13 am #8405
That code is written for our PWM Motor Controllers, which take a PWM signal input. Take a look at the RC_Mecanum_Sabertooth sketch for the Sabertooth implementation.May 18, 2021 at 4:07 pm #8401
You can use those Servo Drivers but you will have to modify the Arduino code to send commands to those instead of the Sabertooths. From the datasheet it sounds like you will need to put the drivers in Digital Speed Control mode and send it Modbus ASCII commands from the Arduino. I haven’t tried looking but I would expect you can find some Modbus ASCII Arduino libraries floating around online.
If you can get the servo motors to act as plain DC motors then you can still use the 2×12 though.May 18, 2021 at 8:51 am #8399
Your motors are intended to be operated using a Servo Motor Driver, which they mention in the link you posted (https://robokits.co.in/motor-drives-drivers/encoder-dc-servo/dc-servo-motor-driver-40v-20a-w-t-step-direction-input). It may be possible to bypass the servo part of it and operate as a basic DC motor but I don’t want to speculate on how to hack a motor we’ve never used before. If you can put a constant DC voltage on it and it spins continuously then it will work with DC motor controllers.
That being said, I don’t recommend using the Sabertooth 2×12. We consistently encounter problems with this specific model and we try to avoid using them on our robots. However the 2×12 RC, 2×25, and all other Sabertooth models work great. The next cheaper option available to you is the Roboclaw 2×15 which is also good and has the option of reading encoders and doing closed loop speed control.
For the RC controller you will need at least 3 axes to control a vectoring robot (drive, turn, and strafe).
And no you don’t need relays. You can ignore that stuff.
For lots more information take a look at our Vectoring Robot Support page: https://wiki.sdrobots.com/index.php/Vectoring_Robot_SupportApril 6, 2021 at 8:22 am #8365
We would not recommend removing screws. You can remove the spring, but it will not provide a ratchet/lock of the stick and the rubber boot tends to push the stick back close to center, so you will need to remove the boot too.March 23, 2021 at 2:12 pm #8361
Sorry, we don’t have this product with shielded wire/endsMarch 23, 2021 at 8:17 am #8359
Hi. the motors are not sealed. You will need to build an entire housing to keep it watertight.March 19, 2021 at 7:49 am #8357
Hi. The Maestro servo controllers are not intended to be hooked up to a RC receiver. Its meant to replace the RC receiver. If all you want to do is to increase the PWM pulse width you can get a servo stretcher. It goes in between the RC Rx and the servo and will stretch the servo pulse. We do not sell them, but most RC hobby shops will have them.January 19, 2021 at 10:21 am #8318
OK it looks like you’re using hexadecimal for the drive command but uint8 for the stop command. What if you send the stop command in hex? Try using [53, 44, 52, 7F, 7F, 0, 0, FE] for the stop command.